Intraoperative Beat-to-Beat Pulse Transit Time (PTT) Monitoring via Non-Invasive Piezoelectric/Piezocapacitive Peripheral Sensors Can Predict Changes in Invasively Acquired Blood Pressure in High-Risk Surgical Patients

Figures

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  Figure 1. Example of dual PES/PCS sensor affixed to the index finger.

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  Figure 2. Data collection device for the PES/PCS system.

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  Figure 3. Geometric schematic of the dual PES/PCS sensor system. Described are the main components that track and relay the signals from an incoming force. PVDF = polyvinylidene fluoride.

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  Figure 4. Flowchart of the PW detection pre-processing: (a) The R-peak in the ECG defines the PW onset. (b) The mean PW is identified as a robust template for physiologically plausible PWs in terms of morphology and magnitude. Each PW is then compared with a patient-specific template (green PW) for automatic deselection of non-optimal PWs (e.g., due to motion noise). A PW is rejected if either its Pearson correlation with the template is less than 0.85 or if the difference in normalized magnitude (i.e., area under the curve [AUC]), is greater than 0.5 (red PW). All remaining PWs are defined as valid. (c) For all valid PWs, PTT is calculated as the time from R-peak to the steepest rise in the PW. (d) For R-peaks where a PW is rejected, PTT values are inputted using a 4th order interpolation technique, WENO4. This interpolation is justified by the fact that 95% of all gaps in the PTT signal are less than 10 beats in length.

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  Figure 5. (a) Example of PWPES. (b) Example of PWPCS. (c) Example of PWIBP from a cardiac surgery patient. PWPES and PWPCS are reported as arbitrary units (a.u.). PWIBP is reported as mmHg.

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  Figure 6. (a) Example of PWPES. (b) Example of PWPCS. (c) Example of PWIBP from a urological surgery patient. PWPES and PWPCS are reported as arbitrary units (a.u.). PWIBP is reported as mmHg.

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  Figure 7. Example of (a) intraoperative SBPIBP (red), DBPIBP (green), and MAPIBP (yellow), (b) 1/PTTPES, (c) 1/PTTPCS, from a cardiac surgery patient.

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  Figure 8. Example of (a) intraoperative SBPIBP (red), DBPIBP (green), and MAPIBP (yellow), (b) 1/PTTPES, (c) 1/PTTPCS, from an abdominal surgery patient.

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  Figure 9. Example of (a) intraoperative SBPIBP (red), DBPIBP (green), and MAPIBP (yellow), (b) 1/PTTPES, (c) 1/PTTPCS, from a urological surgery patient.

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  Figure 10. Boxplot of the Pearson correlation between SBPIBP, MAPIBP, and DBPIBP with 1/PTTPES and 1/PTTPCS.

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  Figure 11. AUROC curves detailing 1/PTT changes detected with PES/PCS sensors with changes in SBPIBP: (a) delta of 1/PTTPCS with decrease in SBPIBP, (b) delta of 1/PTTPCS with increase in SBPIBP, (c) delta of 1/PTTPES with decrease in SBPIBP, (d) delta of 1/PTTPCS with increase in SBPIBP.